[Feature Request] site-wide temporary alert header

[JasonBarahan]

Description

Implement an alert banner for anything that may warrant such things (for example, a campus incident that may affect a CSSU event).

I don't think using it to advertise CSSU events would be useful (though we could make a non-alert banner for this type of advertising if needed/wanted)

Rationale

This should be implemented as doing so allows site visitors to be more aware of what is happening on campus. This should also catch their attention fairly quickly.

Implementation

Alerts are best advertised with yellow background, black text. Anything else is up to whoever takes the ticket

[FakeDeepLearner]

I'll get to it eventually. I believe it should be positioned absolutely at the top of every page, so it doesn't interfere with the positions of anything else